From my experience and the experience of my colleagues this is simply not the case. The vast majority of my clients are sensible in there approach to divorce proceedings and rightly prioritise issues such as any children.
I have never dealt with a case where I have been asked to seek ownership of Airmiles or loyalty points. I believe that couples seeking a divorce are generally very measured in their approach and with some guidance on legal procedures and practices are able to resolve matters in a relatively amicable fashion.
Obviously there will always be the case that is acrimonious and involves extensive court battles but these are thankfully in the minority. I personally do not believe that loyalty points are a "deal-breaker" for many couples.
Within any separation it is important for all parties to consider which assets are a priority for them and focus on the needs of the parties moving forward. It may be that my clients are generally sensible enough not to wage war over such issues or could it be that they are simply not loyal enough to any particular supermarket for it to make any real difference to their financial situation?